Dental amalgam toxicity
||This article needs more medical references for verification or relies too heavily on primary sources. (December 2013)|
Dental amalgam toxicity is mercury poisoning and other toxicity that is purported by some to result from the use of amalgam in dental fillings. Discussion on the topic of amalgam includes debates on whether amalgam should be used, with critics arguing that its toxic effects make it unsafe. Some critics further say that if amalgam was used in the past, then it should be removed from the mouth to protect a person's health.
Other groups say that amalgam can be safely used and should not be removed from anyone's mouth.
Those who advocate the use of amalgam point out that it is durable, relatively inexpensive, and easy to use. On average, resin composites last only half as long as dental amalgam (although modern composites are improving in strength) and dental porcelain is much more expensive. However, the gap between amalgam and composites may be closing. Further, concerns have been raised about the endocrine disrupting (in particular, estrogen-mimicking) effects of plastic chemicals such as bisphenol A used in composite resins. Arguably, there is more credible evidence of a possible subclinical toxic effect of composite resins compared to dental amalgam.
In addition to health and ethics issues, opponents of dental amalgam fillings point to the negative externalities of water contamination and environmental damage of mercury. This concern is especially worrisome since its use and disposal by dentists go largely unregulated in many places, including the United States. The WHO reports that in the United Kingdom mercury from amalgam and laboratory devices accounts for 53% of total mercury emissions. Separators may dramatically decrease the release of mercury into the public sewer system, where dental amalgams contribute one-third of the mercury waste, but they are not required by some states in the United States.
- 1 Classification
- 2 Symptoms
- 3 Causes
- 4 Mechanism
- 5 Prevention
- 6 Treatment
- 7 Epidemiology
- 8 History
- 9 Society and culture
- 9.1 Organizational statements
- 9.2 Regulation by country
- 9.3 Public awareness
- 9.4 Environmental impact
- 10 Research directions
- 11 References
- 12 External links
The toxicity of the amalgam is discussed in terms of the amount of mercury entering the person.
Scientists agree that dental amalgam fillings leach mercury into the mouth, but studies report widely different amounts, which may or may not be sufficient to pose a significant risk to health. Estimates range from 1-3 micrograms (µg) per day (FDA) to 27 µg/day (Patterson). The effects of that amount of exposure are also disputed.
The amount of mercury that patients are subjected to is itself controversial. Many studies have been conducted and findings have varied substantially. Depending on the study, average systemic uptake levels have been estimated to range between 1.7 µg/day and 17 µg/day.
As a (straight) comparison, these daily absorption levels comprise between 3.4% and 68% of workplace air quality safety standards (which range from 25 to 50 micrograms per cubic meter of air).
Critics point out that: (1) the workplace safety standards are based on allowable maxima in the workplace, not mercury body burden; (2) the workplace safety numbers are not applicable to continuous 24hr exposure, they're limited to a normal work day and 40 hr work-week; and (3) the uptake/absorption numbers are averages and not worst case patients (those most at risk). /day
The current recommendations for residential exposure are as follows: The ATSDR Action Level for indoor mercury vapor in residential settings is 1 µg/m3 and the ATSDR MRL (Minimal Risk Level) for chronic exposure is 0.2 µg/m3  According to the ATSDR, the MRL(Minimal Risk Level) is an estimate of the level of daily exposure to a substance that is unlikely to cause adverse non-cancerous health effects. The Action Level is defined as an indoor air concentration of mercury that would prompt officials to consider implementing response actions. It is a recommendation and does not necessarily imply toxicity or health risks. Breathing air with a concentration of 0.2 µg mercury/m3 would lead to an inhaled amount of approximately 4 µg/day (respiratory volume of 20m3/day). 80% of the inhaled mercury vapor is absorbed.
A study conducted by measuring the intraoral vapor levels over a 24-hour period in patients with at least nine amalgam restorations showed the average daily dose of inhaled mercury vapor was 1.7 µg (range from 0.4 to 4.4 µg), which is approximately only 3.4% of the threshold limit value of the OSHA maximum allowable environmental level of 50 µg/day in the workplace, 8.5 times the ATSDR MRL, and 1.7 times the ATSDR Action Level for residential settings. The World Health Organization (WHO) notes that exposure can be greatly increased by personal habits such as bruxism and gum-chewing and cites a report which found a 5.3 fold increase in mercury levels after chewing, eating, or toothbrushing. They report that amalgam is estimated to contribute 50% of mercury exposure in adults. In a WHO report, daily mercury vapor exposure estimates range from 1.2 μg/day to 27 μg/day with the majority of people in the US and Canada being exposed to less than 5 μg/day. However, there is a wide variation between individuals and uptake of up to 100 µg/day has been observed in extreme cases.
A Swedish study of autopsies examined the mercury levels in brains and kidneys and found a strong correlation with the number of amalgam fillings. A German study found that mercury urinary excretion was significantly higher in those with dental amalgam fillings.
The NIDR Amalgam Study performed on a cohort of an adult military population of 1127 healthy males found that, based on their cross-sectional data it is estimated that, on average, each ten-surface increase in amalgam exposure is associated with an increase of 1 ug/L mercury in urine concentration. 
Research on monkeys has shown that mercury released from dental amalgam restorations is absorbed and accumulates in various organs such as the kidney, brain, lung, liver, gastro-intestinal tract, the exocrine glands. It was also found to have crossed the placental barrier in pregnant rats and shown to cross the gastrointestinal mucosa when amalgam particles are swallowed after amalgam insertion or after removal of old amalgam fillings.
Peer-reviewed scientific studies have come to opposite conclusions on whether the mercury exposure from amalgam fillings causes health problems. A 2004 systematic review conducted by the Life Sciences Research Office, whose clients include the FDA and NIH, concluded that "the current data are insufficient to support an association between mercury release from dental amalgam and the various complaints that have been attributed to this restoration material". A peer-reviewed Journal of the Canadian Dental Association article holds that "it seems likely that humans may have evolved with a threshold level for mercury below which there is no response or observable adverse health effects". Another review published in 2005 by the Freiburg University Institute for Environmental Medicine found that "mercury from dental amalgam may lead to nephrotoxicity, neurobehavioural changes, autoimmunity, oxidative stress, autism, skin and mucosa alterations or non-specific symptoms and complaints", that "Alzheimer's disease or multiple sclerosis has also been linked to low-dose mercury exposure", and that "removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials."
Potential amalgam-induced health risks which have been studied by researchers include those related to allergy as well as toxicity. In 2002, the Food and Drug Administration issued a statement on dental amalgam which asserted that "no valid scientific evidence has shown that amalgams cause harm to patients with dental restorations, except in the rare case of allergy". A 1991-1997 study of 3162 patients in Sweden and Germany found that 719 of those with mercury fillings, or 23 percent, tested positive for systemic allergic sensitivity to inorganic mercury on the MELISA lymphocyte proliferation test. In a smaller group of 85 patients who suffered from symptoms resembling Chronic Fatigue Syndrome and had their amalgams replaced with composites and metal-free ceramics, "over 78 percent reported improvement in health status as compared to the period prior to metal removal." A paper published as part of a 1991 National Institutes of Health conference on side-effects of dental restorative materials reported a 22.53% incidence of allergy in subjects who had amalgam fillings for more than five years. Despite these findings, the ADA claimed as recently as 2004 that there had been less than 100 reported cases of allergic reactions to amalgam fillings.
The FDI World Dental Federation performed a meta-analysis of the literature on mercury toxicity and concluded that there is no documented scientific evidence to show adverse effects from mercury in amalgam restorations except in extremely rare cases of mercury hypersensitivity.
In 1991 the United States Food and Drug Administration concluded that "none of the data presented show a direct hazard to humans from dental amalgams." The Food and Drug Administration in 2008 subsequently issued an advisory warning pregnant women and children about dental amalgam containing mercury, and posted this warning on their website. On February 18, 2003, the New York Supreme Court dismissed two amalgam-related lawsuits against organized dentistry, stating the plaintiffs had "failed to show a 'cognizable cause of action'." The plaintiffs blamed the ADA, the New York Dental Association and the Fifth District Dental Society for deceiving the "public about health risks allegedly associated with dental amalgam."
- Studies on humans and animals have demonstrated that dental amalgam contributes significantly to mercury body burden in humans with amalgam fillings.
- Dental amalgam is the most common form of exposure to elemental mercury in the general population, constituting a potentially significant source of exposure to elemental mercury, with estimates of daily intake from amalgam restorations ranging from 1 to 12.5 μg/day, the majority of dental amalgam holders being exposed to less than 5 μg mercury/day.
- Intestinal absorption varies greatly among the various forms of mercury, with elemental mercury (as found in amalgam) being the least absorbed form (<0.01%)
- Absorption also varies according to individual factors such as gum chewing and bruxism (tooth grinding).
- The number of restorations - amalgam or otherwise - is declining, largely due to improved dental hygiene, in all industrialised countries examined declining by 38% since the 1970s in the USA and over 65% in the ten years from 1986 in the UK
- Although several studies have demonstrated that some mercury from amalgam fillings is absorbed, no relationship was observed between the mercury release from amalgam fillings and the mercury concentration in basal brain.
- However, in the same report it was concluded that "...even at very low mercury levels, subtle changes in visual system function can be measured."
- In multiple sclerosis patients with amalgam fillings, red blood cells, haemoglobin, hematocrit, thyroxine (T4), T-lymphocytes and T-8 (CD8) suppressors cells levels are significantly lower, while blood urea nitrogen and hair mercury levels are significantly higher.
- The report also notes that regarding elemental mercury exposure, the main form of exposure from dental amalgam," most studies rely on assessment of exposure at the time of study, which may not be fully informative, as mercury has a long half-life in the body and thus accumulates in continuous exposure ", making the evaluation of effects on health uncertain.
Other lesser findings were reported, including a cross-sectional study in which cognitive function was not related to the number or surface area of occlusal dental amalgams, a case-control study in which patients with numerous amalgam fillings exhibited higher levels of neurological symptoms than the controls, and a study of self-referred patients who believed they were suffering ill-effects from dental amalgams which found no correlation between number of dental fillings and symptomatology, but higher mean neuroticism than two comparison groups (the authors concluded that self-referred patients with health complaints attributed to dental amalgam are a heterogeneous group of patients who suffer multiple symptoms and frequently have mental disorders).
Dental amalgam has been found to be a frequent contributor to oral lichenoid lesions and is possibly a variable associated with an increased risk of other autoimmune conditions such as multiple sclerosis, lupus, thyroiditis and eczema.
Health effects for dentists
In 1991 Geir Bjørklund published a toxicological risk analysis of occupational diseases in dentistry that are related to chronic exposure to inorganic mercury, especially metallic mercury vapour. He found studies indicated that dental work involving mercury may be an occupational hazard with respect to reproductive processes, glioblastoma (brain cancer), renal function changes, allergies and immunotoxicological effects.
In 1994 Rowland found a 40% decline in fecundability in a case controlled study of female dental assistants exposed to mercury in dental offices.It should be noted that female dental assistants exposed to low levels of mercury were more fertile than their unexposed counterparts. There has been no evidence that dentists who are exposed to dental amalgam and vapor on a daily basis get mercury poisoning; however, individual dentists and staff members have become mercury poisoned and studies of the dental profession has documented a decline in cognitive abilities greater than the non-mercury exposed individuals. Some studies have indicated that mercury from dental amalgam has mild effects on some dentists. Dentists in several large-scale studies performed multiple cognitive tests and, compared to a normal population, lagged behind in many areas. A small-scale study based in Singapore found the "exposed-dentist" group had 14% worse scores in memory, co-ordination, motor speed and concentration compared to the control group. The study did not demonstrate any link between mercury exposure and these lagging scores, however. A newer study also found a link between cognitive impairment (including mood) and dental work, even though "exposure among these dental personnel is not much greater than exposures to the general population through the dental amalgam in their fillings" as shown by urinary studies. Twelve of 13 symptoms were correlated with greater mercury exposure.
A study examining the health effects of mercury on dentists in the UK published in the Occupational and Environmental Medicine Journal concluded that 180 dentists had on average 4 times the urinary mercury excretion levels of 180 people in a control group. Dentists were significantly more likely than control subjects to have had disorders of the kidney or memory disturbance. No direct correlation between urinary mercury levels and the disability, however, was found. Urine testing is unreliable for showing lifetime mercury accumulation rather than recent exposure.
There is debate about the circumstances under which dental amalgams may cause mercury poisoning.
The toxicity, when it happens, happens due to mercury poisoning and health effects are a result of the same.
The mechanism by means of which dental amalgams might leak mercury is less clear.
Removal of dental filling containing amalgam
The American College of Medical Toxicology and the American Academy of Clinical Toxicology say that research confirms that mercury from amalgams does not cause illness because the amount of mercury that they release is not enough to cause a health problem. In response to some people wanting their existing amalgam removed for fear of mercury poisoning, these societies advise that the removal of filling is likely to cause a greater exposure to mercury than leaving the fillings in place. These societies warn that removal of amalgam fillings, in addition to being unnecessary health care and likely to cause more mercury exposure than leaving them in place, is expensive.
Using alternative dental material
Alternative materials which may be suitable in some situations include composite resins, glass ionomer cements, and gold alloys. Most of these materials, with the notable exception of gold, have not been used as long as amalgam, and some are known to contain other potentially hazardous compounds. This is why biocompatibility testing is recommended for all dental materials as per ADA/ANSA or ISO standards, and can be performed by specialized laboratories. Teaching of amalgam techniques to dental students is declining in some schools in favor of composite resin, and at least one school, University of Nijmegen in the Netherlands, had eliminated dental amalgam from the curriculum entirely in 2001. This is largely a response to consumer pressure for white fillings for cosmetic reasons, and also because of the increasing longevity of modern resin composites.
Anti amalgam sources typically promote removal of amalgam fillings and substitution with other materials. Detoxification may also be advised, including fasting, restricted dieting to avoid mercury containing foods, and quasi-chelation therapies, allegedly to remove accumulated mercury from the body.
Consumer Reports magazine claims that the connection between many of these diseases and amalgam fillings is solely revenue-generating propaganda. Consumer Reports told its readers on several occasions that "if a dentist wants to remove your fillings because they contain mercury, watch your wallet."
Far more mercury is released when amalgam fillings are removed than their entire lifetime if left undisturbed. This led to some dentists who advocate removal of amalgam fillings (who may describe themselves as "holistic dentists") to develop special techniques to counter this, such as wearing breathing apparatus, using high volume aspiration, and performing the procedure as quickly as possible. The impact of such techniques on the dose of mercury received during filling removal is unknown, and have been criticized as merely advertising gimmicks which enables such dentists to charge far more than a normal dentist would for the same procedure. Sources of mercury from the diet, and the potential harm of the composite resins (which mimic female sex hormones) to replace the purportedly harmful amalgam fillings are also ignored by these dentists.
Over a lifetime, dietary sources of mercury are far higher than would ever be received from the presence of amalgam fillings in the mouth. For example, due to pollution of the world's seas and oceans with heavy metals, products such as cod liver oil may contain significant levels of mercury.
Better dental health overall coupled with increased demand for more modern alternatives such as resin composite fillings (which match the tooth color), as well as public concern about the mercury content of dental amalgam, have resulted in a steady decline in dental amalgam in developed countries, though overall amalgam use continues to rise worldwide. Given its superior strength, durability and long life relative to the more expensive composite fillings, it will likely be around for many more years to come.
||The examples and perspective in this article may not represent a worldwide view of the subject. (June 2010)|
Dental amalgam, an alloy of about 50 percent elemental mercury, was first introduced in France in the early 19th century. Chosen for its cost-effective durability, this amalgam is a source of low-level exposure to mercury vapour, and an enormous amount of controversy. Although the vast majority of patients with amalgam fillings are exposed to levels believed to be too low to pose any risk to health, many patients (i.e., those in the upper 99.9 percentile) exhibit urine test results that are comparable to those at the maximum allowable legal limits for workplace (occupational) safety. Nonetheless, in the United States the National Institutes of Health has stated that amalgam fillings pose no personal health risk, and that replacement by non-amalgam fillings is not indicated. In Norway, amalgam fillings are banned due to concerns over public health and environmental pollution.
In 1840, the American Society of Dental Surgeons was founded by a group of dentists who met in New York city. It was the only national organization of dentists in existence at the time. Chapin A. Harris, the co-founder of the ASDS and the first dental school in the US, the Baltimore College of Dental Surgery, spoke of dental amalgam in his opening address: "It is one of the most objectionable articles for filling teeth that can be employed, and yet from the wonderful virtues ascribed to this pernicious compound by those who used it, thousands were induced to try its efficacy". In 1845, the ASDS had members sign a mandatory pledge promising not to use mercury fillings because of fear of mercury poisoning in patients and dentists (at the time, dentists made amalgam by mixing liquid mercury and the other components of amalgam themselves in their office, a practice which continued until pre-filled amalgam capsules became generally available in the 1960s). During the next decade some members of the society were suspended for the use of amalgam. Because of its stance against dental amalgam , membership in the American Society of Dental Surgeons declined, and due to the loss of members, the organization disbanded in 1856.
In 1859, the American Dental Association (ADA) was founded by twenty-six delegates representing various dental societies in the United States at a meeting in Niagara Falls, New York. The ADA did not forbid use of amalgams. The ADA position on the safety of amalgam has remained consistent since its foundation. As of 2006, the ADA has over 152,000 members and is the largest and longest-standing professional association of dentists in the world.
Amalgam formulations and properties were gradually improved, notably by Dr. G.V. Black in 1895. Despite these changes, debate over the use of amalgams persisted in the dental profession. The ADA maintained until 1984 that mercury was bound in amalgam and did not release mercury vapor. In the 1970s studies demonstrated that a small amount of mercury vapor was constantly being released from amalgam, corroborating the first such study published in 1882 in the Ohio State Journal of Dental Science by Dr. Eugene S. Talbot.
Controversy over the mercury component of dental amalgam dates back to its inception, when it was opposed by the United States dental establishment, but it became a prominent debate in the late 20th century, with consumer and regulatory pressure to eliminate it "at an all-time high". In a 2006 nationwide poll, 76% of Americans were unaware that mercury is the primary component in amalgam fillings, and this lack of informed consent was the most consistent issue raised in a recent U.S. Food and Drug Administration (FDA) panel on the issue by panel members. Environmental concerns over external costs exist as well, as the use of dental amalgam is unregulated at the federal level in, for example, the United States. The WHO reports that in the United Kingdom mercury from amalgam accounts for 5% of total mercury emissions and that when combined with waste mercury from laboratory and medical devices, represents 53% of total mercury emissions. Separators may dramatically decrease the release of mercury into the public sewer system, where dental amalgams contribute one-third of the mercury waste. Although several states (NJ, NY, MI, etc.) require the installation of dental amalgam separators, they are not required by the United States government. As of 2008, the use of dental amalgam has been banned in Norway, Sweden and Denmark, and a U.S. FDA committee has refused to ratify assertions of safety.
In the 1990s, several governments evaluated the effects of dental amalgam and concluded that the most likely health effects would be due to hypersensitivity or allergy. Germany, Austria, and Canada recommended against placing amalgam in certain individuals such as pregnant women, children, those with renal dysfunction, and those with an allergy to metals. In 2004, the Life Sciences Research Office analyzed studies related to dental amalgam published after 1996. Concluding that mean urinary mercury concentration (μg of Hg/L in urine, HgU) was the most reliable estimate of mercury exposure, it found that those with dental amalgam were unlikely to reach the levels where adverse effects are seen from occupational exposure (35 μg HgU). 95% of study participants had μg HgU below 4-5. Chewing gum, particularly for nicotine, along with more amalgam, seemed to pose the greatest risk of increasing exposure; one gum-chewer had 24.8 μg HgU. Studies have shown that the amount of mercury released during normal chewing is extremely low. However, from reviewing medical literature, the World Health Organization (WHO) states mercury levels in biomarkers such as urine, blood, or hair do not represent levels in critical organs and tissues. Additionally, Gattineni et al. found that mercury levels do not correlate with the number or severity of symptoms. It concluded that there was not enough evidence to support or refute many of the other claims such as increased risk of autoimmune disorders, but stated that the broad and nonspecific illness attributed to dental amalgam is not supported by the data. Mutter in Germany, however, concludes that "removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials."
Society and culture
American Dental Association (ADA)
The American Dental Association (ADA) has asserted that dental amalgam is safe since its foundation in 1859. In its advisory opinion to Rule 5.A. of the ADA Code of Ethics, it has also held that, "the removal of amalgam restorations from the non-allergic patient for the alleged purpose of removing toxic substances from the body, when such treatment is performed solely at the recommendation or suggestion of the dentist, is improper and unethical". According to the Boston College Law School study, "A dentist who is found guilty of violating the ADA Code of Ethics can be sentenced, censured, suspended, or expelled from the ADA" and the "ADA forbids its dentists from suggesting mercury removal under threat of license suspension". The same study pointed out that state dental associations and disciplinary boards have "not only adopted the ADA's position as a matter of routine" in proceedings which have sanctioned anti-amalgam dentists or stripped them of their licenses in California, Maryland, Arizona, Colorado, and Minnesota, but in many cases "the board members themselves often belonged to the ADA as well". A 2002 article in the Atlanta Journal and Constitution reported allegations by anti-amalgamists that the ADA had effectively imposed gag rules which forbade them from discussing their positions with patients. The Boston College Law School study also cites proceedings in which an Arizona dentist, "is facing sanctions for advocating alternative materials", a California dentist lost his license, "for running an advertisement entitled: "Mercury Emission from Silver Filings Unsafe by Government Standards", and a Maryland dentist, "was sanctioned for writing an article on dental amalgam removal". More recently, the ADA has entered into litigation "aimed at defending its reputation and discouraging further lawsuits by patient-plaintiffs against dental amalgam".
After FDA’s deliberations and review of hundreds of scientific studies relating to the safety of dental amalgam, the FDA concluded that "clinical studies have not established a causal link between dental amalgam and adverse health effects in adults and children age six and older." The FDA concluded that individuals age six and older are not at risk to mercury-associated health affects from mercury vapor exposure that come from dental amalgam. ADA states that "dental amalgam has an established record of safety and effectiveness, which the scientific community has extensively reviewed and affirmed." The ADA also encourages dental offices to follow its best management practices for amalgam waste, which will in turn reduce discharges of used dental amalgam into dental offices' waste water.
On the controversy of dental amalgam toxicity, the ADA asserts the best scientific evidence supports the safety of dental amalgam. Clinical studies have not established an occasional connection between dental amalgam and adverse health effects in the general population.
The recent WHO report reaffirms the safety and importance of maintaining the availability of dental amalgam. The comments of the ADA concluded that dental amalgam remains an excellent and valuable restorative material for both dentists and patients; other alternative tooth restorative materials haven’t been proven to be as effective as dental amalgam.
The comments of the ADA state that there is no scientific reason to revisit the 2009 FDA ruling; while high exposure to elemental mercury has been associated to adverse health effects, the mercury exposure in dental amalgam is not high enough to cause harm in patients. Dental amalgam is a safe restorative material which now have special controls on this device, imposed by the FDA to ensure the safety and effectiveness of dental amalgam. Also, in the FDA final regulation on dental amalgam in 2009, the FDA recommended the product labeling of dental amalgam. The suggested labeling included: a warning against the use of dental amalgam in patients with mercury allergy, a warning that dental professionals use appropriate ventilation when handling dental amalgam, and a statement discussion of scientific evidence on dental amalgam’s risks and benefits in order to make informed decisions amongst patient and professional dentists.
The Dental Material Commission
In 2002, Maths Berlin, Professor Emeritus of Environmental Medicine and Chair of the 1991 World Health Organization Task Group on Environmental Health Criteria for Inorganic Mercury, led The Dental Material Commission as it published an overview and assessment of the scientific literature published between November 1997 – 2002 as part of a special investigation for the Swedish Government on amalgam related health issues. The 2002 report was a follow-up to a similar review of the literature published between 1993 and November 1997. The 2002 review assessed over 700 references. A final report was submitted to the Swedish Government on 3 June 2003 and included Berlin's report as an annex to the full report. Berlin's annex was translated into English and is currently available from the Government Offices of Sweden along with an introduction and summary of the full report. Berlin's 2002 review includes a summary of the 1997 analysis. In the final report Berlin considers dental amalgam to be an unsuitable filling material and recommends eliminating amalgam in dentistry for medical and environmental reasons.
International Academy of Oral Medicine and Toxicology (IAOMT)
The IAOMT educates dentists on safely handling and disposing of mercury-laden amalgam fillings, and developed safe forms of effective dental treatment in many areas, including periodontics and preventing oral disease. The IAOMT has researched and reported on the danger of mercury in amalgam fillings to the health and safety of patients, dental workers, and the environment. Researchers Dr. Mark and David Geier reanalyzed the data from the "Portugal children's amalgam trial" study (originally published in the Journal of the American Medical Association). The study purported prove the safety of mercury amalgam, but Mark and Geier say the data shows show a dose-dependent toxicity in a key metabolic system. They conclude that mercury "silver" fillings block basic functions of cells when placed in children's teeth.
Notable critics of amalgam fillings
Alfred Stock, a noted chemist, reported becoming very ill, and eventually tracing his illness to his amalgam fillings and the resulting mercury intoxication. He described his recovery after the fillings were removed and believed that amalgam fillings would come to be seen as a "sin against humanity." Hal Huggins, a Colorado dentist (previous to having his license revoked), is a notable critic of dental amalgams and other dental therapies he believes to be harmful; his views on amalgam toxicity were featured on 60 Minutes.
Regulation by country
The use of mercury in dental fillings is approved in most countries. Due to health risks, environmental concerns, and popular demand, some legislators have introduced legislation to prohibit or restrict use of amalgam fillings. In many countries, unused dental amalgam after a treatment is subject to strict disposal protocols, again for possible environmental reasons rather than for fear of direct toxicity to humans. Over 100 countries are signatories to the United Nations “Minamata Convention on Mercury”. The treaty has not banned the use of dental amalgam, but allows to phase down amalgam use over a time period appropriate to domestic needs, an approach advocated by the World Health Organisation (WHO).
Sewers from Norwegian dental clinics older than 1994 (or if there is other reason to believe amalgam have ended up in the sewers instead of the patients mouth) shall be cleaned by experienced personnel to properly remove any residual mercury. The detailed procedure to do so is available from Norwegian Pollution Control Authority free of charge.
Amalgam use is illegal in Sweden as of 1995. The Swedish amalgam ban is for both environmental and health issues, according to the Swedish authorities. The Swedish Chemicals Inspectorate (KemI) maintains a web site containing a report on the investigation for a general ban on mercury on which it states, "KemI judges that there are strong grounds for banning amalgam for environmental reasons. From a health point of view there is every reason to apply a precautionary approach."
Canada is a signatory to the United Nations “Minamata Convention on Mercury”. Amalgam use is legal in Canada, but the government has a reference exposure level (REL) for mercury guideline which it uses to study risk. The Canadian Health Measures Survey (CHMS) of 5,604 Canadians aged 6 years to 79 years collected data on the number of tooth surfaces restored with dental amalgam and urine analysis for mercury concentration (UHg), providing a direct measure of the incremental increase in UHg per amalgam-filled tooth surface. The results of this study show that about 64% of all Canadians (age 6 and older) have at least one amalgam-restored tooth surface. "Altogether the Canadians have about 191 million amalgam surfaces, representing about 76.4 million amalgam-restored teeth. The total mass of Hg carried in those teeth is approximately 38 metric tons. Of Canadians with dental amalgam restorations, 80.4% experience a daily dose of Hg that exceeds the Canadian REL-associated dose. The number of amalgam surfaces that will not result in exceeding the REL-associated dose varied from two amalgam surfaces (children, both sexes) to seven surfaces (adult males)."
In the US, many states are undertaking both regulatory and non-regulatory activities to ensure proper management of mercury-containing dental amalgam.
In the United States, amalgams are classified as a "device," not a "substance," by the Food and Drug Administration (FDA). Under the U.S. Code of Federal Regulations, amalgams are a prosthetic device:
- Amalgam Alloy, (a) Identification. An amalgam alloy is a device that consists of a metallic substance intended to be mixed with mercury to form filling material for treatment of dental caries. (b) Classification. Class II. (21 CFR 872.3050 (2001))
On July 28, 2009, FDA issued a final rule that: (1) reclassified mercury from a class I (least risk) device to class II (more risk) device; (2) classified dental amalgam as a class II device; and (3) designated a special controls guidance document for dental amalgam.
The special controls guidance document recommends specific labelling, including an Information for Use statement "Dental amalgam has been demonstrated to be an effective restorative material that has benefits in terms of strength, marginal integrity, suitability for large occlusal surfaces, and durability. Dental amalgam also releases low levels of mercury vapor, a chemical that at high exposure levels is well documented to cause neurological and renal adverse health effects." 
In 2001 in a lawsuit involving California Proposition 65 and amalgams, a California Superior Court judge ruled that all dental offices with more than nine employees must provide notices on the contents of dental fillings. The mandated notice reads:
- Notice to Patients, Proposition 65: Warning on dental amalgams, used in many dental fillings, causes exposure to mercury, a chemical known to the state of California to cause birth defects or other reproductive harm. Root canal treatments and restorations including fillings, crowns and bridges, use chemicals known to the state of California to cause cancer. The U.S. Food and Drug Administration has studied the situation and approved for use all dental restorative materials. Consult your dentist to determine which materials are appropriate for your treatment.
Following the meeting of the joint committees on 6–7 September 2006, when the panel of outside advisers that the FDA had asked to assess the conclusions of its report on amalgam safety rejected the FDA report in a 13-7 vote, they stated the report's conclusions were "unreasonable", given the quantity and quality of information currently available. Panelists said remaining uncertainties about the risk of so-called silver fillings demanded further research, in particular, on the effects of mercury-laden fillings on children and the fetuses of pregnant women with fillings and the release of mercury vapor on insertion and removal of mercury fillings. Michael Aschner, a professor of pediatrics and pharmacology at Vanderbilt University and a panel consultant said "There are too many things we don't know, too many things that were excluded."
Shortly after the decision of the joint advisory panel, the president of the International Academy of Oral Medicine and Toxicology (IAOMT) wrote to the FDA to ask for an expanded review of current science on dental amalgams, a definitive date for such a hearing, and a format that will assure that the full breadth of health effects is assessed. In a press release the ADA wrote that it " welcomes the call by a U.S. Food and Drug Administration (FDA) panel for additional review of scientific studies on the safety of dental amalgam fillings." and reiterated that "the overwhelming weight of scientific evidence supports the safety and efficacy of dental amalgam, and it should continue to be made available to dentists and their patients " and " dental amalgam contains elemental mercury combined with other metals such as silver, copper, tin and zinc to form a safe, stable alloy."
A 2006 Zogby International poll of 2,590 US adults found that 72% of respondents were not aware that mercury was a main component of dental amalgam and 92% of respondents would prefer to be told about mercury in dental amalgam before receiving it as a filling. A 1993 study published in FDA Consumer found that 50% of Americans believed fillings containing mercury caused health problems. Some dentists (including a member of the FDA's Dental Products Panel) suggest that there is an obligation to inform patients that amalgam contains mercury.
The broad lack of knowledge that existed among the public was displayed when a December 1990 episode of the CBS news program "60 Minutes" covered mercury in amalgam. This resulted in a nationwide amalgam scare and additional research into mercury release from amalgam. The following month Consumer Reports published an article criticizing the content of the broadcast, stating that it contained a great deal of false information and that the ADA spokesperson on the program was ill prepared to defend the claims.[clarification needed]
The WHO reports that mercury from amalgam and laboratory devices accounts for 53% of total mercury emissions, and that one-third of the mercury in the sewage system comes from dental amalgam flushed down the drain. Mercury is an environmental toxin and the World Health Organization, OSHA, and NIOSH have established specific occupational exposure limits. Amalgam removed from teeth is classified as toxic waste in various countries, but in many countries it is not regulated, including the United States. The environmental pollution of mercury imposes health risks upon the surrounding population; in economics this pollution is considered an external cost not factored into the private costs of using dental amalgam. Separators may dramatically decrease the release of mercury into the public sewer system, but they are not required in the United States.
Environmental risks are mitigated provided that amalgams are disposed of properly. ISO has issued standards regarding the proper handling and disposal of amalgam waste, and legislation to enforce these standards is being adopted in some US states.
Mercury loading of municipal wastewater
The Association of Metropolitan Sewerage Agencies (AMSA) studied seven major waste-water treatment plants and found that dental uses were "by far" the greatest contributors of mercury load, on average contributing 40%, over 3 times the next greatest contributor. The EPA recognizes dental amalgam as a major source of the mercury in the water. The Western Lake Superior Sanitary District that dentists emit .1 grams of mercury per day per dentist. Based on this, dental amalgam contributes 14% of the mercury in Seattle and 12% of the mercury in San Francisco. 4% of the mercury in Lake Superior is believed to originate from amalgam. The National Association of Clean Water Agencies noted in a report that purification of mercury from waste water will impose a significant financial burden upon municipal treatment plants. Several other groups have analyzed mercury in waste water and concluded that it is a serious problem. Other studies have shown this to be a gross exaggeration. With respect to pollution in the United States, a study done in 1992 showed that batteries "accounted for 86 percent of discarded mercury and dental amalgam a mere 0.56 percent."
Cremation of bodies containing amalgam restorations results in near-complete emission of the mercury to the atmosphere, as the temperature in cremation is far greater than the boiling point of mercury. In countries with high cremation rates (such as the United Kingdom), mercury has become a great concern. Proposals to remedy the situation have ranged from removing amalgam-containing teeth prior to cremation to installing activated carbon adsorption or other post-combustion mercury capture technology in the flue gas stream. These proposals range from unpopular to expensive.
In the US, there is no regulation of mercury at the state or national levels. The cremation industry denies that there even exists an issue and uses data from a much discredited and outdated report, refusing to consider the more recent and accurate data.
Mercury emissions from cremation are growing rapidly in the US, both because cremation rates are increasing and because the number of teeth in the deceased is increasing due to better dental care. False teeth, of course, have no dental restorations, while natural teeth can have a variety of restorations. Since amalgam restorations are very durable and relatively inexpensive, many of the older deceased have amalgam restorations. According to work done in Great Britain, mercury emissions from cremation are expected to increased until at least 2020. Exact data are not available for the US, but testimony before Congress in 2010 by the Mercury Policy Project/Tides Center provided the following conclusion:
In a U.K. report from 2003, it was estimated that the amount of mercury per cremation would increase by 42% from 2005 to 2020, based solely on the increased number of teeth – and hence restorations, per person. If the same would apply in the United States, the total amount of mercury emitted would increase by 160% due to a 83% increase in the number of cremations and a 42% increase in mercury per cremation. Thus, rather than 6,516 pounds a year, the total mercury emission would be about 16,944 pounds per year.xviii 
Unfortunately, the US cremation industry refuses to even discuss the issue with an open mind and both US citizens and the world load of mercury from cremation continues to increase each year.
The proper interpretation of the data on hand is, to date, controversial. The vast majority of past studies have concluded, not without controversy, that amalgams are safe. However, although the vast majority of patients with amalgam fillings are exposed to levels too low to pose a risk to health, many patients (i.e. those in the upper 99.9 percentile) exhibit urine test results which are comparable to the maximum allowable legal limits for long-term work place (occupational) safety. Two recent randomized clinical trials in children  discovered no statistically significant differences in adverse neuropsychological or renal effects observed over the five-year period in children whose caries were restored using dental amalgam or composite materials. In contrast, one study showed a trend of higher dental treatment need later in children with composite dental fillings, and thus, claimed that amalgam fillings are more durable. However, the other study (published in JAMA) cites increased mercury blood levels in children with amalgam fillings. The study states, "during follow-up [blood mercury levels were] 1.0 to 1.5 μg higher in the amalgam group than in the composite group." EPA considers high blood mercury levels to be harmful to the fetus, and also states that "exposure at high levels can harm the brain, heart, kidneys, lungs, and immune system of people of all ages." Currently, EPA has set the "safe" mercury exposure level to be at 5.8 μg of mercury per one liter of blood. While mercury fillings themselves do not increase mercury levels above "safe" levels, they have been shown to contribute to such increase. However, such studies were unable to find any negative neurobehavioral effects.
During the FDA's December 13–14, 2010 CDRH panel review of the International Academy of Oral Medicine and Toxicology's request for reconsideration to the classification of amalgam, neurologists questioned the type of neurobehavorial tests and the unethical nature of a prospective trial looking for brain damage in children. Furthermore, evidence was presented by the Geier's that further analysis of the data found that an unusual porphyrin called Coproporphyrinogen indicative of pathophysiology (harm) was found in a dose response relationship to the number and size of amalgams placed, thus calling into question the claim that no injury had occurred.
As a result of a lawsuit, a fund was developed to research amalgam-related illness, and a clinical trial evaluating the effect of removing amalgam was published in 2008. The trial found that all groups had improved symptoms, including a group where the participants were treated with a "biological detoxification" therapy and dental amalgam was not removed. Follow-up of a clinical trial was published in 2010.
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